The invention relates to a device and a method having a charging unit and a vehicle for inductive power transmission from the charging unit to the vehicle, in which the charging unit comprises a primary coil and the vehicle comprises a secondary coil, and in which the primary coil generates a magnetic transmission field in a transmission range between the primary coil and the secondary coil.
Inductive power transmission systems are known from the prior art. FR 2 947 114 A1, for example, describes an induction charging device for a vehicle for charging an electrical energy storage mechanism in the vehicle, the induction charging device consists of a ground unit having a primary coil and an automotive unit having a secondary coil.
An induction charging device for an electric vehicle is designed for power transmission in the range of several kilowatts.
One object of the invention is to describe an improved device and an improved method having a charging unit and a vehicle for inductive power transmission from the charging unit to the vehicle.
Advantageous embodiments and refinements of the invention are derived from the dependent claims.
According to the invention, the vehicle has a sensor unit for monitoring the temperature in the transmission range and the charging unit comprises a control device which controls the transmission power in a charging operation as a function of a result of the temperature monitoring.
A charging operation is understood in particular to be the time segment during which there is a transmission of electric power from the charging unit to the vehicle. The control device controls and/or regulates the transmission power from the chronological beginning until the chronological end of the charging operation. The result of the temperature monitoring by the control unit serves as the input variable for the control and/or the regulation.
According to a preferred embodiment of the invention, the sensor unit is designed as an infrared detector system, which has a thermal resolution limit and a spatial resolution limit, such that an object having thermal properties above the thermal resolution limit and spatial properties above the spatial resolution limit is designated as a critical object, and a critical object situated in the transmission range can be detected by the infrared detector system.
If the critical object is detected by the infrared detector system, this detection is considered as the result of the temperature monitoring. In the case when no critical object is detected by the infrared detector system, this is considered as the result of the temperature monitoring.
This means that a critical object situated in the transmission range during a charging operation can be detected by the infrared detector system if it exceeds the thermal resolution limit of the infrared detector system, i.e., in particular has a sufficiently high temperature for detectability by the infrared detector system, and in combination therewith, exceeds the spatial resolution limit of the infrared detector system, i.e., in particular has a sufficiently large spatial extent for detectability by the infrared detector system.
The infrared detector system has an at least unidirectional communication setup to the control unit. In this way, a signal can be transmitted to the control unit when a critical object is detected by the infrared detector system. The signal transmitted may result in a control measure by the control unit, for example, an interruption in generation of a transmission field by the primary coil.
According to another variant of the invention, in a charging operation, the transmission power is adjustable at a first rate of power increase by the control unit, and in a charging operation, the transmission power is adjustable by the control unit at a second rate of power increase, such that the second rate of power increase exceeds the first rate of power increase.
The rate of power increase indicates the transmission power per unit of time. Thus, at the second rate of power increase, there is a faster increase in the transmission power over time by a certain amount than is the case at the setting of the first rate of power increase.
Furthermore, it is advantageous if, at the first rate of power increase, a standard object situated in the transmission range can be heated by the transmission field over a critical period of time if the standard object becomes a critical object within the critical period of time and, after detection of the standard object by the infrared detector system, the power increase in the transmission range can be interrupted by the control unit and/or the transmission power can be reduced.
With this device, a method comprising the following steps can be carried out. First, in a charging operation, the transmission power is increased by the control unit at the first rate of power increase during the critical period of time. After the critical period of time, the transmission power is increased by the control unit at the second rate of power increase. If a critical object is detected by the infrared detector system during the charging operation during the critical period of time or even after the critical period of time, the power increase in the transmission range is interrupted by the control unit and/or the transmission power in the transmission range is reduced by the control unit and/or a warning signal is output by the control unit or by the vehicle.
The invention is based on the considerations explained below:
For electrified vehicles, there are known methods which permit a non-contact, preferably inductive charging of the vehicle electric system and/or of the storage mechanism containing the same.
Since the energy transmission in inductive charging can be disturbed by metallic or electrically-conductive materials between the two sides of the non-contact transmission, measures are to be taken which detect such objects or materials and ensure countermeasures such as an interruption in the power transmission. This successfully prevents unwanted heating of the foreign bodies and possible negative consequences.
The monitoring methods known according to the prior art are either inadequate because overheating of very small or thin-walled conductive materials such as a metal film, for example, are not detected reliably or promptly. Exclusion of any potential threat due to overheating or foreign bodies, the vehicle or the vehicle surroundings, however, has the highest priority. Or the monitoring methods have a high degree of complexity so that additional cost-intensive and space-intensive hardware might be needed.
A measure is proposed which makes use of monitoring methods present in the prior art in combination with a targeted transmission power control in inductive charging for foreign body identification of particularly small and thin-walled conductors.
This measure presupposes that a vehicle is equipped with a vehicle-side inductive charging system. The vehicle charging system has as its main component in particular a secondary coil, with which electric power can be transmitted to the vehicle from a primary coil external to the vehicle. The inductive charging system of the vehicle comprises a sensory system, e.g., infrared sensors with which at least large foreign bodies in the power transmission range having a critically high temperature can be detected. Foreign bodies are to be expected in particular on and/or in the vicinity of the primary coil using the arrangement of the primary coil as an energy transmitter on the road surface and the secondary coil as an energy receiver on the vehicle underbody, and are to be evaluated critically with regard to unwanted energy absorption, which may result in an increase in temperature.
One disadvantage here is that large and solid conducting bodies in the energy transmission range can be detected securely and reliably using an infrared sensor system but small or very thin-walled conductors (e.g., parts of beverage packagings having a conductive coating) can be heated so rapidly in the energy transmission range that reaching the resolution limit of the infrared sensor system, i.e., the initial detection of elevated temperature takes place only when local combustion, for example, begins on the thin-walled conductor or on surrounding materials. The occurrence of such a state is to be avoided in any case, such that its probability of occurrence is increased, for example, by a spatially unfavorable orientation with initially thermal insulation of parts of the foreign body with respect to the infrared system (for example, turning the aluminum coating, which is in the energy transmission range, away from the infrared system in the case of a beverage carton). In this example, the local energy absorption by the aluminum coating is perhaps detected only when parts of the beverage carton might have already been damaged thermally. This is true in particular of the condition when energy transmission acts directly on the foreign body in its full intensity.
This disadvantage is counteracted by the fact that due to the reduction in energy transmission intensity, primarily due to a power control over time in inductive charging, heating of the foreign body is reduced to such an extent that, on the one hand, the sensor system can detect the unwanted heating and, on the other hand, a critical threshold is not reached (e.g., ignition temperature, injury threshold in subsequent contact the foreign body). In addition, it is possible through a sufficiently gradual power control over time to achieve the result that the heating (possibly very local) of the foreign body is adequately distributed over larger regions of the foreign body, so that the resolution limit of the monitoring sensor system is reached and reliably detects the larger region. The power control may be linear over time, continuous or in increments.
Advantages include the increase in the probability of detection of foreign bodies and thus the reduction in risk of damage in performing inductive charging. This increase can also be achieved in a neutral manner with regard to design space and weight, i.e., without the use of additional hardware.
A preferred exemplary embodiment of the invention is described below on the basis of the accompanying drawing. This yields additional details, preferred embodiments and refinements of the invention. In detail, this shows schematically
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawing.